Contact time adjustment for mechanical rectifiers



E. J. DIEBOLD July 29, 1958 CONTACT TIME ADJUSTMENT FOR MECHANICAL RECTIFIERS Filed Aug. 29. 1952 6 Sheets-Sheet l p i z,

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CONTACT TIME ADJUSTMENT FOR MECHANICAL RECTIFIERS Filed Aug. 29. 1952 6 Sheets-Sheet 6 .4 5 :95 F619 K/ M A/ United States Patent CONTACT TIME ADJUSTMENT FOR MECHANICAL RECTIFEERS Edward John Diebold, Ardmore, Pa., assignor to I-T E Circuit Breaker Company, Philadelphia, Pin, a corporation of Pennsylvania Application August 29, 1952, Serial No. 307,024

7 Claims. (Cl. 321--43) My invention relates to mechanical converter or rectifiers of the type set forth in copending application Serial No. 212,017, filed February 21, 1951, now Patent No. 2,693,569, and is more particularly directed to a structural arrangement whereby contact time adjustment can be made by means of a stationary adjustment means While the converter or rectifier is running and under load.

A mechanical converter produces direct voltage by making metallic contact between a proper phase of an A. C. system and the associated D. C. system during the time interval the particular phase of the A. C. system is capable of delivering energy in the desired direction and breaking the metallic contact when the A. C. phase reverses its voltage in relationship to the D. C. voltage. This operation is performed sequentially and repeatedly insynchronism with the A. C. frequency.

With the structure of my invention contact time adjustment is provided to compensate for accumulated inaccuracies in manufacturing and for wear and to obtain exact time required for operation. This adjustment is made by modifying the length of individual push-rods and is accomplished with precision While the machine is running and under load.

The structure of my invention for adjusting the contact timing comprises a push rod with internal threading at its lower end to receive an adjusting screw which is externally threaded. The push rod has an external spline which meshes with an internal spline on a Worm gear. The worm gear is positioned to have no longitudinal movement, with its motion restricted to rotational movement. The worm gear is controlled by a worm which terminates outside the mechanism housing. The adjusting screw is constructed at its lower end in a manner so that it is limited to vertical movement. Hence, manual rotation of the worm gear, through the cooperating splines, will rotate the push rod. Since the adjusting screw cannot rotate, the rotation of the push rod will move it toward or away from the adjusting screw due to the threaded engagement therebetween. Hence, the effective length of the push rod is rapidly and easily adjusted by means of a worm which remains stationary with respect to the vertical oscillation of the push rod.

An oscilloscope is placed across the contact converter and an oscillogram of the voltage conditions thereacross are obtained. By means of a comparison with a diagram of the desired voltage configuration, the operator can rapidly determine whether or not the mechanical converter is operating with proper overload safety, no load safety and sufiicient contact time of engagement and disengagement.

A tabulation chart is used by the operator in coordination with the oscillogram and diagram of desired voltage configuration to permit the operator to determine which contact connect push rod assembly must be adjusted to make the oscillogram conform to the diagram of the desired voltage configuration. Hence, by this means a simple, rapid and etiective procedure is utilized to enable ice the operator to make the proper adjustment of the length of the push rod assemblies.

A primary object of my invention is the provision of stationary means for contact time adjustment while the rectifier is running.

Another object of my invention is to provide means contact time adjustment for a mechanical rectifier 'to compensate for accumulated inaccuracies in manufacture and for wear.

Still another object of my invention is to provide adjustment means for a mechanical rectifier whereby the effective length of the contact push-rod can be adjusted from stationary means while it has vertical oscillatory motion.

A further object of my invention is a mechanical rectifier with adjustment means to obtain the exact time required for operation, with the adjustment means being operative while the rectifier is running and under load.

Another object of my invention is a mechanical rectifier contact time adjustment means whereby each bridging contact comprising the contact between each phase bus of the source and the positive and negative bus of the load can be repeatedly and independently adjusted and altered.

A further object of my invention is to provide individual contact time adjustment for each of the bridging contacts of a mechanical rectifier while the unit is operating under load conditions.

Another object of my invention is to provide adjustment means to modify the length of individual push rods with precision while the machine is running and under load.

Another object of my invention is to provide a visual indicator to the operator to enable him to rapidly and effectively make the proper adjustment of the push rod assembly.

A further object of my invention is to provide an oscilloscope arrangement by which the operator has a guide to indicate which contact assembly should be adjusted.

A still further object of my invention is to provide a novel push rod assembly adjustment means which can be properly adjusted in accordance with a comparison of an oscillogram of the voltage across the contact converter and a diagram of the desired voltage configuration.

These and other objects of my invention will be apparent from the appending description taken in connection with the drawings in which:

Figure 1 is a schematic electrical connection diagram of a single mechanical rectifier unit in which my invention is used showing the attachment of the oscilloscope to the contact converter.

Figure 2 is a perspective view of the control of the push rod and its eiiect on the contact engagement and disengagement.

Figure 3 is an exploded perspective view showing the novel contact time adjustment means of my invention.

Figure 4 is an exploded perspective view of the replaceable contact assembly used with my invention.

Figure 5 is a cross-section view of the assembled replaceable contact assembly of Figure 4.

Figure 6 is a side detailed view of the push rod and associated removable and replaceable contact assembly.

Figure 7 is a top view of Figure 6 illustrating the arrangement and assembly of the removable and replace- 42 drives an eccentric 43.

of Figure 9 with the contact structure effecting the various positions thereof.

In Figure 1, the source of alternating current is taken r from the alternating current lines 10 through the circuit breaker 11 to step down transformer 12. The source current is then passed through the commutatingreactors 13 to step the current for switching purposes as set sequentially and repeatedly in synchronism with the A. C. frequency connects the alternating current source buses 10a, b, c to the D. C. load buses -21.

The contact converter 15 is bridge connected to permit better use of the power transformer 12 by doubling the phase operation of the connector and thereby result in smoother D. C. current and less interference with commutation facilities as best seen in Figures 2, 6 and 7.

The bridge connected contact converter 15 has two sets of contacts, a negative set -30-27 (a--) in contact block 71 and a positive set 26-31-28 (a+) in contact block 70. 180 electrical degrees from each other and the con- The two sets of contacts are 011 set tacts in either positive or negative set for all the phases a, b and c are set 120 apart. The circuit may be supplied with three phase voltage a, b and c and at one period of time the load current will flow from phase a through contact a+ through the load and back over a contact c to phase c. During positive commutation between phases a and b, the load current divides between these two phases by closed contacts a+ and b+.

For the purpose of simplification, I have shown in Figure 2 the switching structure which is used at phase a,

. it being understood that the switch apparatus for phases 7 b and c are identical in construction, as seen in Figure 7.

An excited type synchronous motor 40 is energized from the three phase source voltage a, b, c and drives shaft 41. A cam 42 is integrally attached to the shaft 41 and therefore driven by the motor 40. The cam The eccentric member 43 is pinned to bell cranks -51 by means of pin 52.

. Since the bell cranks 50-51 are rotatably mounted by hearing 54 on a fixed overlap control shaft 54, the movement imparted to eccentric 43 by cam 42 is a reciprocating motion which in turn is imparted to the bell cranks 50-51.

The cross extension arms of the bell cranks 50-51 'are connected by rocker arm pins -61 which serve as the driving means for push rods 62 and 63. The rocker arm pins 60-61 are connected to extending arms 50-51 by means of bearing 60-61 so that these pins 60-61 have a rotational movement to enable them to maintain constant engagement with the push rods 62-63 as will Y hereinafter be more fully described.

Push rods 62 and 63 are identical in construction and t are shown in the exploded detailed view of Figure 3 and in the detailed side view of Figure 6. Upward movement of push rod 62, imparted thereto by the rocker arm pin 60 will urge the movable disc shaped bridging contact 31 against the bias of contact spring 81 and thereby disengage it from engagement with stationary A. C. contact 28 and stationary D. C.+ contact The construction and operation of the repla'cable contact structure -71 is illustrated in Figures 4, 5 and 7 and explained in detail in copending application Ser. No.

307,067, filed August 29, 1952, now Patent No. 2,798,909.

The structure and operation of the adjustable push rod 62 will best be understood from the following description taken in connection with the exploded detailed 4 view of Figure 3 and the detailed side view of Figure 6. The push rod 100 is provided with external splines 101 at its lower portion and an insulated heat 102 at its upper portion. The reduced cross-sectional head 103 and the enlarged cross-sectional portion 104 of insulating head 102 are sufiiciently small to move through the opening provided by the space between stationary contacts 26-28' to thereby enable the head 103 to engage the bridging contact ring 31. Hence, when the contact rod 100 is moved upward by the rocker arm pin 60 or 61 the reduced cross-sectional portion 103 of the insulating head 102 will be driven through the inside diameter of the stationary contacts 25-27 or 26-28 and portions 103 will engage the lower surface of the ring contact 30 or 31 and urge it upward against the bias of contact spring or 81 to contact disengaged position.

The insulating material 102 is designed to prevent the movable contact 30 or 31 from moving away from the stationary contacts with an oscillatory motion to thereby prevent delayed contact separation which would decrease the safety portion of the step.

External splines 101 located at the lower edge of the contact rod mesh with the internal splines 105 of the worm gear 106. Hence, the push rod 100 has vertical movement with respect to the worm gear 106 but is restricted from having rotational movement with respect thereto due to the mesh of splines 101 and 105. The worm gear 106 as will hereinafter be more fully explained has no vertical movement and is restricted to rotational movement. The worm gear 106 is in mesh with the worm 108 which is controlled by the shaft 109 as seen in Figures 2 and 3. Hence, manual rotation of shaft 109 will rotate worm 108. The mesh engagement between worm 108 and worm gear 106 will cause worm 109 to rotate the worm gear 106. The mesh engagement of the internal splines 105 of worm gear 106 with the external splines 101 of push rod 100 will cause rotational movement of the push rod 100 due to the rotational movement of worm gear 106. As will hereinafter be more fully explained, rotational movement of push rod 100 will cause the adjusting screw 110 to thread toward or away from the push rod 100. Thus, rotation of the worm 108 will cause a change in the over-all length of the push rod 62.

The lower portion of push rod 100 is hollow and has a threaded internal portion 111. The internal threads 111 mesh with the external threads of the adjusting screw 110. Near the lower portion of the adjusting screw 110 is a flange 112 which acts as a stop or rest for the return spring cap 113. The return spring 116 is concentric with the adjusting screw 110 and is seated at its lower end against the return spring cap 113 and at its upper end against the stationary ledge 107. The lower end of the adjusting screw 110 is provided with a slot 117 that registers with the key or projection 118 on rocker arm pin 60.

The engagement of projection 118 with slot 117 prevents rotational movement of the adjusting screw 110 so that its motion is limited to vertical movement. Thus, during operation of the rectifier the synchronous motor 40 oscillates the pin 60 through eccentric 43 and bell cranks 50-51 and causes the push rod 100 and attached adjusting screw 110 to move as a single unit.

As heretofore noted the rocker pins 60 and 61 are mounted in bearing 60' and 61 of extension arms 50 and 51. The projection slot engagement 117-118 between the push rod 62 and rocker pin arm 61 are always in engagement due to the force of return spring 116 and the rotational movement of the pins 61 permitted by the bearing 61' as seen in Figure 6.

A detailed view of the support mounting and construction of the push rod of Figure 3 is shown in Figure 6.

A housing serves as a guide and vertical support for the push rod 100. Anti-friction bearing 126-127 on the push rod 100 serve as the physical support and guide for the vertical movement of the push rod means 62. The push rod 62 is force fed lubricated by means of oil which is fed into the area between the rod 100 and the housing 125 through port 128 from oil chamber 129. A plurality of oil drip shields 130, 131, 132 are attached to the upper portion of the push rod 100. The oil drip shield 130, 131, 132 function in a well known manner to prevent excess oil from reaching the insulating head 103 and thereby prevent any oil from reaching the bridging electrical contact 30. Return holes 135 are provided to return the excess oil through the hollow interior of the push rod 100.

The entire push rod assembly 62 of removable contact assembly 71 and housing means 125 are supported by stationary structures 141 and 142. The lower stationary structure 141 has an extension member 107 which serves as a bearing support for the worm gear 106 and also as the upper seat for the return spring 116. The extension 145 of stationary support structure 141 serves as the support for the housing member 125. The flange 148 on the housing 125 abuts the stop bushing 149 of support 145. The flange 148 also serves as the upper abutment for the worm gear spring 150, the lower end of this spring resting on the worm gear 106 to continuously urge the gear 106 into engagement with the bushing 107.

Thus, the operation of push rod assembly 62 and 63 is as follows: rotation of the synchronous motor 40 oscillates the bell crank member 50-51 about the fixed axis 54. The sliding engagement between slot and pin 117- 118 of the push rod and rocker arm pin 60 or 61 plus the guide of housing 125 imparts only vertical movement to the push rod 100. Since the push rod assemblies 62 and 63 are mounted on opposite ends of the bell crank 50-51, they will be 180 out of phase with each other. At a predetermined position of the upstroke the insulating head 103 will engage the bridging contact 30 and move it upward against the downward bias of the 150 pound contact spring 80 and thereby interrupt the circuit between phase bus 100: at stationary contact 27 and the D. C. negative bus at contact 25. The bridging contact 30 will remain disengaged from these stationary contacts -27 during the remaining portion of the upstroke and for a predetermined time or distance of the down stroke travel of the push rod assembly 62.

It will therefore be apparent that for a given R. P. M. of the synchronous motor 40 the time of contact engagement and disengagement and length of time that the contacts remain engaged and disengaged will be a function of the efiective length of the push rod assembly 62-63.

As heretofore noted adjustment to modify the length of the individual push rod assemblies 62 and 63 for phases I a, b and c is accomplished by means of worm 108 and worm gear 106. The worm gear 106 is continuously urged against the bushing 107 by means of hold-down spring 150 and hence has no vertical motion either independently or with the push rod 100.

Thus, when the rectifier is operating, the spline mesh 105-111 between the worm gear 106 and push rod 100 permits the rocker arm pin 61 to oscillate the push rod assembly 62 in a vertical path while the worm gear 106 remains stationary. Hence, while the machine is running and under load, the worm gear 106 and worm 108 will remain stationary and thereby be available for adjustment to modify the efiective length of the push rod 62. Rotation of the worm gear 106 by the operators rotation of worm 108-109 will cause the push rod 100 to rotate due to mesh therebetween at splines 105-109. However, since the adjustment screw 110 is keyed to the rocker arm or 61 and held in right engagement therewith by means of return spring 116, the adjustment screw 110 will not be rotated by the rotation of worm gear 106. Hence, the push rod 100 will be threaded toward or away from the adjustment screw 110, depending on the direction of rotation of the worm 108, to thereby alter the effective length of push rod assembly 62.

As best seen in Figures 7 and 8, six bridging contact structures may be used in a unit to rectify 5,000 amperes. That is, a pair of contact assemblies and push rod assemblies are provided for each phase a, b, c of the source to alternately connect it to the positive and negative buses 20-21 of the load. Thus, each unit switching each phase either to positive or negative can be independently and individually adjusted to modify the length of the push rod and achieve proper contact time adjustment.

As fully set forth in copending application Serial No. 212,017, filed February 21, 1951, the mechanical converter will operate at its greatest efiiciency when the contact converter 15 causes contact engagement and disengagement at the proper time during the current stepping operation caused by the commutating reactor 13. Hence, with the apparatus of my invention the push rod assembly 62 can be modified in length to adjust for contact time engagement and disengagement and length of time of contact engagement and disengagement to insure maximum efliciency of operation and proper overload and no load safety.

As best seen in Figures 1 and 8, the contact converter 15 is an assembly which contains the plurality of contact blocks for each phase. For example in phase A, contact blocks 70a and 71a are provided for contact conversion to the negative D. C. bus 21 and the positive D. C. bus 20, respectively.

As seen in Figure 1, an oscilloscope 200 is connected to the selector switch 201. Leads 202, 203, 204, 205 and 206 connect the selector switch 201 to the station ary A. C. and D. C. contacts of the contact assemblies 70 and 7 011. Hence, by means of the selector switch 201, the oscilloscope 200 can be selectively connected across the stationary contacts of contact assemblies 71a, 71b, 70a, 70b etc.

It will be noted that when the proper adjustments of the pre-excitation winding of the commutating reactor 13 and the connecting rod of the push rod assemblies 62, 63 have been made, the voltage configuration seen on the oscillogram of oscilloscope 200 will be identical for all of the contact assemblies. The desired configuration of the voltage across the stationary contacts is best seen in Figure 9.

When the selector switch 201 is positioned to connect the oscilloscope 200 across stationary contacts 25-27 of contact block 71a, the voltage will be fiat when contact 71a is closed, as seen to the left of the oscillogram of Figure 9.

The tabulation chart, as seen in Figure 10, is used in co-ordination with the configuration on the oscillogram to indicate to the operator the particular components which cause various configurations at the various times indicated.

For example, with the selector switch 201 positioned to connect the oscilloscope 200 across the stationary contacts of contact assembly 71a, the left vertical column, under position of selector switch 201, of the tabulation chart of Figure 10 is used.

Thus, for example, as seen in either extreme and or left hand end columns of the chart, time A represents the opening or break of the movable contact 30 with the pair of stationary contacts 25-27 of contact block 71a.

The voltage configuration between times A and B is caused by the break coil of the commutating reactor 13 and is fully described in my copending application Serial No. 212,017, filed February 21, 1951. Thus, time B represents the end of the break step for contact block 71a. At time C, as can readily be determined from the tabulation chart of Figure 10, the step length for the contact block 70a begins.

For the purposes of adjusting the magnitude of preexcitation of the commutating reactor 13, the operator investigates the configuration of the voltage between times K and M. As clearly set forth in the above mentioned application, the magnitude of the relatively horizontal creased or decreased.

For the purposes of this invention, namely contact time adjustment, the operator is primarily concerned with the configuration of the voltage between times K and M and is particularly interested in the configuration at time contact.

As may be observed from the chart 10, the pip that occurs at time contact is indicative of the mechanical break or opening of the contacts at 70a.

As best seen in the ideal curve of Figure 9, it is desirable to have the pip (the disengagement of the contacts at 70a) between times K and M occur after /3 of the time between K annd M. That is, it is desirable to have Vs of the step length created by the commutating reactor 13a elapse before the movable contact is disengaged from the stationary contacts at 70a, assuring proper overload safety. Hence, the /3 distance between times K and L represent overload safety.

On the other hand the overload safety period should not be greater than one third of the step length of the time between K and M.

The reason for this is that the time elapse between L and M represents the time that the contacts of 70a must disengage and deionize so that the arc will not strike at time M. V

Thus, the time period between L and M must be sufficiently long to permit de-ionization of the atmosphere between the movable and stationary contacts of contact block 70a. Hence, this region between times L and M v is the no load safety period. Thus, when the oscilloscope 20 is connected across stationary contacts of block 71a, the operator can readily determine whether the associated contact block 70a is being disengaged at the proper time within its step length period K and M.

In the event that the overload safety period K and L and the no load safety period L through M did not favorably compare with the desired voltage configuration curve of Figure 9, the effective length of the push rod assembly 63 can be modified by the adjustment means, 109 108, in the manner heretofore described.

It will be noted that the time elapse between C and L will represent the length of contact time engagement 7 of the contacts at 7011: and the time elapse between N and A will represent the length of time of contact engagement of the contacts 71a.

Thus, it will be apparent as above described that the oscilloscope 200 connected across the stationary contacts of contact block 71a will enable the operator to determine the time when the contacts 70a will open (pip at time L). Hence, the period of contact 70a engagement and time of contact 70a disengagement can be readily and easily modified and adjusted by the operator.

Thus, in similar manner, with the oscilloscope 200 connected across the contacts 700 by means of the selective switch 201, the period of contact engagement (N-A) and disengagement of contacts 71a can be modified by adjustment means 109', 108 of push rod assembly 62 in a manner heretofore described.

In summary, I have provided a novel contact push rod assembly with adjustment means which remain stationary during the vertical oscillatory movement of the assembly.

By providing an oscilloscope which can be selectively connected across any one of the six sets of contact converters, the operator can rapidly and easily determine whether or not the time or period of time of contact ennovel adjustment means.

In the foregoing I have described my invention only in connection with preferred specific embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim: 1. In a mechanical converter providing a unidirectional current, a push rod assembly comprising a push rod and an adjusting screw; adjustment means connected to cause relative movement between said push rod and said adjustment screw to modify the effective length thereof, said adjustment means remaining stationary during the running of said mechanical converter and means to impart vertical motion to said push rod assembly andprevent rotation of said adjusting screw.

2. In a mechanical converter providing a unidirectional current, a push rod assembly comprising a push rod and an adjusting screw; adjustment means comprising a Worm and a worm gear, said worm gear having splines on the internal surface thereof, said push rod having splines on the external surface thereof, said worm gear splines and said push rod splines being in mesh engagement, said adjustment screw being threaded externally, said push rod being threaded internally, said external threads of said adjustment screw being in mesh engagement with said internal threads of said push rod, means to impart vertical motion to said push rod assembly and prevent rotation of said adjusting screw.

3. In a converter having cooperating contacts comprising stationary contacts and a movable contact, means to bias said movable contact into engagement with said stationary contact, a rotatable shaft and eccentric thereon connected to control the movement of a push rod assembly in a first direction, said push rod engaging and disengaging said movable contact during running operation of said converter, said push rod effective to move said movable contact against the force of said means to effect contact disengagement, said push rod assembly comprising a push rod and adjusting screw, time of contact engagement and disengagement determined by the effective total length of said push rod and adjusting screw, adjustment means to modify the effective length prising stationary contacts and a movable contact, means to bias said movable contact into engagement with said stationary contact, a rotatable shaft and eccentric thereon connected to control the movement of a push rod assembly in a first direction, said push rod engaging and disengaging said movable contact during running operation of said converter, said push rod effective to move said movable contact against'the force of said means to eflfect contact disengagement, said push rod assembly comprising a push rod and adjusting screw, time of contact engagement and disengagement determined by the effective total length of said push rod and adjusting screw, adjustment means to modify the effective length of said push rod assembly during operation of said push rod assembly, said adjustment means being independent of the movement of said rotatable shaft and eccentric thereon, said eccentric being operatively connected to said adjusting screw to impart vertical motion to said push rod assembly and prevent rotation of said adjusting screw.

5. In a mechanical converter for energizing a D.-.C. load from a multiphase A.-C. source comprising commutating reactors, contact converters, an oscilloscope, and a plurality of push rod assemblies, each of said converters comprising a pair of stationary and a bridging moveable contact therefor, each of said push rod assemblies connected to cause engagement and disengagement of said movable contact with said stationary contact of its respective contact converter, each phase of said A.-C. source being connected in series with one of said commutating reactors, the stationary contacts of one of said contact converters and said D.-C. load, said oscilloscope connected across at least one of said pair of stationary contacts, adjustment means to alter the effective length of said push rod assembly, alteration of the effective length of said push rod being effective to alter the oscillogram of said oscilloscope.

6. In a mechanical converter providing a unidirectional current by synchronously engaging and disengaging a pair of contacts connected in series with said A.-C. load, a push rod assembly comprising a push rod and an adjusting screw; said push rod being operable to engage 15 and disengage said pair of contacts adjustment means connected to cause relative movement between said push rod and said adjustment screw to modify the effective length thereof, said adjustment means remaining stationary during the running of said mechanical converter, an oscilloscope across said contacts of said mechanical converter, the oscillogram of said oscilloscope being a measure of the point of disengagement of said contacts.

7. The method of altering the effective length of a mechanical converter push rod assembly comprising the steps of selectively connecting an oscilloscope across the stationary contacts of a mechanical converter and varying the elfective length of the push rod assembly until the oscillogram of said oscilloscope achieves a predetermined configuration.

References Cited in the file of this patent UNITED STATES PATENTS 2,227,937 Koppelmann Ian. 7, 1941 2,375,416 Kuber May 8, 1945 2,622,234 Blatter Dec. 16, 1952 

